This application claims the priority of German Patent Application Serial No. 100 57 311.8, filed Nov. 17, 2000, the subject matter of which is incorporated herein by reference.
The present invention relates, in general, to a bumper for a motor vehicle, and in particular to a bumper of a type having an U-shaped cross member for attachment to longitudinal members of a vehicle chassis, wherein the cross member includes a web and two legs connected to the web.
Bumpers are arranged across the front and rear of a motor vehicle between the plastic casing, forming an end piece of the body, and the chassis of the motor vehicle, and are provided to prevent damage in the event of a low speed impact. Oftentimes, impact absorbers, so called crash boxes, are disposed between the cross member and the longitudinal members, to absorb the energy in the event of a collision by converting the impact energy into deformation work.
German Pat. No. DE 42 38 631 A1 describes a bumper assembly with an impact absorber made of an inner tube and an outer tube, which move into one another in the event of a collision. The inner tube is secured to the legs of the cross member. This bumper assembly suffers shortcomings as a result of its weight and complex construction.
U.S. Pat. No. 3,599,757 discloses various embodiments of impact absorbers.
An impact absorber is also known which has a rectangular construction and is composed of an upper shell element and a lower shell element. The shell elements have a U-shaped profile and are joined together. The cross member proximal end is either secured to the web of the cross member or to the ends of the lateral legs. This area, however, represents a potential weak spot because a deformation of the bumper may result in a separation of the joint between the impact absorber and the cross member.
It would therefore be desirable and advantageous to provide an improved bumper which obviates prior art shortcomings and includes a cross member of enhanced rigidity and increased mechanical stability.
According to one aspect of the present invention, a bumper for a motor vehicle; includes a cross member having a U-shaped cross section and intended for attachment to longitudinal members of a vehicle chassis, wherein the cross member includes a web and two legs connected to the web; and an impact absorber received in the cross member and having a cross member proximal end joined to the web and to confronting ends of the legs.
The present invention resolves prior art problems by joining the impact absorber with its cross member proximal end on the inside to the web of the cross member as well as to the area of the ends of the legs. Suitably, the joint between the impact absorber and the cross member is implemented through a welding process.
Practice has shown that a bumper according to the present invention exhibits significantly higher capability of absorbing energy because the cross member is considerably reinforced and stiffened as a consequence of the connection with the impact absorber. Moreover, the joint is secured to a greater extent from separation, in particular as a result of the welded seams, even when the bumper is subjected to extreme deformations, e.g. in the event of high-speed collisions.
The connection between the impact absorber and the cross member is established by a first joint in substantially parallel relationship to the web as well as by a second joint which extends transversely to the first seam at the end of the legs. This type of connection implemented at least in two planes ensures a high stiffness and mechanical stability.
According to another feature of the present invention, the legs of the cross member may be continued at their ends by flanges which further enhance the rigidity of the cross member. Depending on requirements at hand, the flanges may be turned inwardly or outwardly with respect to the cross member, with the impact absorber exhibiting a complementary configuration when joined to the cross member.
According to another feature of the present invention, the impact absorber may be formed at the cross member proximal end with lateral lobes in spaced-apart relationship to the legs. In this way, weight can be saved, and a fabrication may be implemented more efficiently.
According to another feature of the present invention, the impact absorber may be formed at the cross member proximal end with lateral lobes that are joined with the legs. This construction results in even higher rigidity and stability, which is desired especially when heavy vehicles are involved. Suitably, the cross member proximal end of the impact absorber is joined all-round with the cross member. Of course, joining may be implemented also along partial sections about adjoining cross sectional areas.
The impact absorber involved here has a hollow box-like structure (crash boxes) and may be made of two shell elements representing an upper and a lower shell element. The upper and lower shell elements are joined at the longitudinal edges of their lateral skirts. At their side proximate to the longitudinal members, the shell elements normally have an attachment flange for connection to the longitudinal members.